Lado, Robert
University of Michigan, 1957
Buku Teks
MacMillan/McGraw-Hill , 1997
Buku Teks
Jesness, Jerry, author
Corwin Press, 2004
Buku Teks
Alfonso, Anthony, author
Sophia University LL Center of Applied Linguistics, 1980
Buku Teks
University of Bath, 1985
Buku Referensi